feat: switch DataFrame generic to its schema (#307)

This is a breaking change.

It feels more natural to express the genericness of a DataFrame through
its schema rather than its similarity to a Record of Series. For
example, joins then can be computed more easily, as we don't need to
unpack each Series to rename them.

Author: Ugzuzg

__tests__/type.test.ts

@@ -0,0 +1,109 @@
+import { expectType } from "ts-expect";
+
+import pl from "@polars/index";
+
+describe("type tests", () => {
+  it("types the DataFrame from the input", () => {
+    const df = pl.DataFrame({
+      bools: [false, true, false],
+      bools_nulls: [null, true, false],
+      int: [1, 2, 3],
+      int_nulls: [1, null, 3],
+      bigint: [1n, 2n, 3n],
+      bigint_nulls: [1n, null, 3n],
+      floats: [1.0, 2.0, 3.0],
+      floats_nulls: [1.0, null, 3.0],
+      strings: ["foo", "bar", "ham"],
+      strings_nulls: ["foo", null, "ham"],
+      date: [new Date(), new Date(), new Date()],
+      datetime: [13241324, 12341256, 12341234],
+    });
+
+    expectType<
+      pl.DataFrame<{
+        bools: pl.Bool;
+        bools_nulls: pl.Bool;
+        int: pl.Float64;
+        int_nulls: pl.Float64;
+        bigint: pl.UInt64;
+        bigint_nulls: pl.UInt64;
+        floats: pl.Float64;
+        floats_nulls: pl.Float64;
+        strings: pl.String;
+        strings_nulls: pl.String;
+        date: pl.Datetime;
+        datetime: pl.Float64;
+      }>
+    >(df);
+  });
+
+  it("produces the expected types", () => {
+    const a = pl.DataFrame({
+      id: [1n, 2n],
+      age: [18n, 19n],
+      name: ["A", "B"],
+    });
+    const b = pl.DataFrame({
+      id: [1n, 2n],
+      age: [18n, 19n],
+      fl: [1.3, 3.4],
+    });
+    expectType<pl.Series<pl.UInt64, "age">>(a.getColumn("age"));
+    expectType<
+      (
+        | pl.Series<pl.UInt64, "id">
+        | pl.Series<pl.UInt64, "age">
+        | pl.Series<pl.String, "name">
+      )[]
+    >(a.getColumns());
+    expectType<pl.DataFrame<{ id: pl.UInt64; age: pl.UInt64 }>>(a.drop("name"));
+    expectType<pl.DataFrame<{ id: pl.UInt64 }>>(a.drop(["name", "age"]));
+    expectType<pl.DataFrame<{ id: pl.UInt64 }>>(a.drop("name", "age"));
+    expectType<
+      pl.DataFrame<{
+        id: pl.UInt64;
+        age: pl.UInt64;
+        age_right: pl.UInt64;
+        name: pl.String;
+        fl: pl.Float64;
+      }>
+    >(a.join(b, { on: ["id"] }));
+    expectType<
+      pl.DataFrame<{
+        id: pl.UInt64;
+        age: pl.UInt64;
+        ageRight: pl.UInt64;
+        name: pl.String;
+        fl: pl.Float64;
+      }>
+    >(a.join(b, { on: ["id"], suffix: "Right" }));
+    expectType<
+      pl.DataFrame<{
+        id: pl.UInt64;
+        id_right: pl.UInt64;
+        age: pl.UInt64;
+        name: pl.String;
+        fl: pl.Float64;
+      }>
+    >(a.join(b, { leftOn: "id", rightOn: ["age"] }));
+    expectType<
+      pl.DataFrame<{
+        id: pl.UInt64;
+        id_right: pl.UInt64;
+        age: pl.UInt64;
+        age_right: pl.UInt64;
+        name: pl.String;
+        fl: pl.Float64;
+      }>
+    >(a.join(b, { how: "cross" }));
+  });
+
+  it("folds", () => {
+    const df = pl.DataFrame({
+      a: [2, 1, 3],
+      b: [1, 2, 3],
+      c: [1.0, 2.0, 3.0],
+    });
+    expectType<pl.Series<pl.Float64, string>>(df.fold((s1, s2) => s1.plus(s2)));
+  });
+});

package.json

@@ -62,6 +62,7 @@
     "chance": "^1.1.13",
     "jest": "^29.7.0",
     "source-map-support": "^0.5.21",
+    "ts-expect": "^1.3.0",
     "ts-jest": "^29.3.4",
     "ts-node": "^10.9.2",
     "typedoc": "^0.28.4",